Broadcasting method and broadcast receiver

ABSTRACT

A broadcasting method and a broadcast receiver whereby contents are first distributed only for storage so that the stored contents are later played back in a time period predetermined by the distributing party, the contents being encrypted for protection against unauthorized reproduction in any time period other than the intended one. A content is transmitted together with a begin store command in a first time period for storage onto a storage medium at the receiving side. In a time period subsequent to the first time period, a play command is broadcast so as to get the content retrieved from storage for playback. The content should preferably be encrypted. The encrypted content is decrypted and played back using a decryption key transmitted along with the play command in the second time period. The decryption key is deleted the moment the decryption process is terminated.

CROSS-REFERENCES

This is a continuation application of U.S. Ser. No. 09/942,690, filedAug. 31, 2001, which claims priority to JP 2001-013491, filed Jan. 22,2001. The entire disclosures of all of these applications are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a method for broadcasting contents suchas visual images and audio sounds, as well as to a receiver forreceiving the contents broadcast by that method.

Contents such as visual images and audio sounds (i.e., net informationexcluding added data), to be telecast or transmitted by radioconventionally over such media as cables or radio waves, are broadcastand received simultaneously. In that setup, when to broadcast programsis determined solely by the transmitting side, and the media band widthis monopolized by the contents being transmitted. If any contents aredesired to be broadcast a plurality of times, the entire contents mustbe transmitted as many times.

If the contents are visual images that are digitally compressed, theystill require a broad bandwidth for transmission. One way to ease themonopoly of the media by transmission of such huge data involves havingdigitally compressed and encrypted contents stored on a suitable storagemedium (e.g., DVD) that may be distributed illustratively by mail whilebroadcasting only a decryption key for eventual decryption of thecontents (as proposed by Japanese Published Unexamined PatentApplication, publication No. 11-213553). The decryption key may beacquired by subscribers only.

The proposed way of distributing contents requires that users assubscribers receive both encrypted contents and a decryption key todecrypt the received contents. The users may play back the contentswhenever they want and however they want it. Unlike conventionalbroadcasting, the contents in general are not reproduced by thereceiving side at any specific time dictated by the broadcasting side.

To simultaneously broadcast and receive contents requires securing abroad band width for transmission, as mentioned above. Meanwhile,digitizing contents makes it possible for the distributing party toadopt, besides the above-described use of storage media, variousrational means of distribution such as dividing the contents into aplurality of narrow band widths for transmission, and transmitting thecontents on a narrow band width over an extended period of time. In suchcases, simultaneity is lost. Still, the distributing party (i.e., thebroadcaster) has numerous contents that the broadcaster wants to bereceived at predetermined times by the receiving side. Conventionaltechniques have so far been incapable of embracing such rational meansof distributing contents while meeting the requirement for the contentsto be viewed and/or heard in any intended time.

Where the same contents are to be broadcast a number of times, it may bedesirable to transmit the contents only once before their repeated,predetermined playback so that they may utilize a broad band width asefficiently as possible. However, broadcasting arrangements offeringthese features have yet to be implemented by conventional techniques.

SUMMARY OF THE INVENTION

It is therefore a first object of the present invention to overcome theabove and other deficiencies of the prior art and to provide abroadcasting method and a broadcast receiver whereby contents arebroadcast and received without being viewed on the spot by the receivingside, so that the broadcast contents are later viewed at a timepredetermined by the broadcasting side.

It is a second object of the present invention to provide a broadcastingmethod and a broadcast receiver whereby broadcast contents are protectedagainst being viewed at any time other than the predetermined time bythe broadcasting side.

The first object may be achieved according to one aspect of the presentinvention, which provides a broadcasting method comprising the steps of:broadcasting contents along with a begin store command in a first timeperiod, the begin store command causing the contents to be stored onto astorage medium at a receiving side; and broadcasting a play command in asecond time period subsequent to the first time period, the play commandcausing the contents stored on the storage medium to be retrievedtherefrom for audio and visual playback.

According to another aspect of the invention, there is provided abroadcast receiver comprising: a receiver for receiving contentsbroadcast in a first time period along with a begin store commandcausing the contents to be stored, and a play command broadcast in asecond time period subsequent to the first time period, the play commandcausing the stored contents to be retrieved for playback; a storagemedium for storing the contents received; and a processor for storingthe contents onto the storage medium in accordance with the receivedbegin store command and for retrieving the contents from the storagemedium for playback in accordance with the received play command.

The second object may be achieved by preferably implementing a broadcastreceiver wherein the contents broadcast in the first time period may beencrypted, wherein the play command broadcast in the second time periodmay include a decryption key for decrypting the encrypted contents, andwherein the processor may retrieve the encrypted contents from thestorage medium and decrypt the retrieved contents for playback. In thepreferred setup, the processor may further store the received decryptionkey into a memory and delete the decryption key from the memory afterdecrypting the encrypted contents using the decryption key.

These and other objects, features and advantages of the presentinvention will become more apparent in view of the following detaileddescription of the preferred embodiments in conjunction withaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view explaining a broadcasting method embodyingthe invention;

FIG. 2 is a flowchart of steps constituting the inventive broadcastingmethod for content distribution;

FIG. 3 is a schematic view detailing the step of transmitting encryptedcontents as shown in FIG. 2;

FIG. 4 is a schematic view detailing the step of transmitting a playcommand as shown in FIG. 2;

FIG. 5 is a flowchart of steps outlining how a broadcast receiver ofthis invention works;

FIG. 6 is a block diagram of a typical broadcast receiver embodying thisinvention;

FIG. 7 is a flowchart of steps explaining how encrypted contents arereceived and stored by the broadcast receiver shown in FIG. 6; and

FIG. 8 is a flowchart of steps explaining how a play command is receivedand how the corresponding encrypted content is decrypted and played backby the broadcast receiver of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of this invention will now be described in detailwith reference to the accompanying drawings.

Illustratively, satellite broadcasting is implemented in a setup wheremost of the available channel band width is allocated to a telecast andthe rest of the band width is used to permit a plurality of databroadcasts. In that setup, the remaining band width is further dividedinto parts for the multiple broadcasts, so that each band width part issignificantly narrow. Such a narrow band width, however, is sufficientfor each data transmission. FIG. 1 outlines a broadcasting methodembodying the invention in a way suitable for data broadcasts of theabove type.

In FIG. 1, reference character A denotes a time period ranging frommidnight to early morning, in which normal programming is not in effectbecause of a small number of expected viewers; and reference character Brepresents a time period in which normal programming is in force duringthe day from morning till evening. In this embodiment, at least oneencrypted content 100 is transmitted in the time period A using all bandwidths that would otherwise be allocated to a plurality of databroadcasts. Later in the time period B, liner notes and voicecommentaries are broadcast together with play commands as sub data 101on the content 100. A decryption key for decrypting the encryptedcontent 100 is broadcast as included in each play command. In the timeperiod B, data 102 constituting other broadcasts are transmitted overtheir respective channels.

In the time period A, the encrypted content 100 is received by aconstantly operating receiver and stored on a storage medium at thereceiving side. The stored content 100 is retrieved in accordance witheach play command in the sub data 101 broadcast in a subsequent timeperiod. The retrieved content 100 is played back while being decrypted.

The time at which to broadcast the sub data 101 on the content 100 ispredetermined by the distributing party (broadcasting side). That meansthe content 100 is played back by the receiving side only at the timedesignated beforehand by the distributing party. At any other time, theencrypted content 100 is protected against unauthorized decryption andplayback because play commands are not distributed.

It is possible to broadcast the play command as part of the sub data 101a plurality of times in the time period B. This allows the content 100to be played back as many times using the broadcast play commands. Thatis, the content is broadcast only once while the distributed content maylater be played back as many time as designated.

Below is a detailed description in sequence of how contents aretypically distributed and received.

FIG. 2 is a flowchart of steps constituting the broadcasting methodembodying the invention. Contents 100 are first encrypted (in step 201),and the encrypted contents 100 are transmitted in the time period Apreceding an intended time for playback (in step 202). When the playbacktime predetermined by the distributing party is reached in the timeperiod B, sub data 101 on the contents 100, i.e., liner notes, voicecommentaries and play commands about the contents, are broadcast (instep 203).

The contents 100 are encrypted in step 201 using a different encryptionkey for each content. For example, a content Ci is encrypted by use ofan encryption key KEi unique to the content Ci. That encryption processgenerates an encrypted content KEi(Ci).

FIG. 3 is a schematic view detailing broadcast of a content 100 in thetime period A. The broadcasting side first sends a begin store command501 causing the constantly operating receiver to store the content ontoa storage medium. Transmission of the begin store command 501 isfollowed by CRID(Ci) as an identifier uniquely identifying the contentto follow. The identifier CRID(Ci) is then followed by an encryptedcontent KEi (Ci). At the end of the content, the transmitting side sendsan end store command 504 to terminate broadcast of the content.

FIG. 4 is a schematic view explaining details of sub data 100 on thecontent 100 to be distributed in the subsequent time period B and at atime predetermined by the distributing party. The transmitting sidefirst sends data 701 other than a content, such as liner notes and voicecommentaries on the content KEi (Ci). The data 701 are followed by aplay command 702 causing the encrypted content KEi (Ci) to be playedback from the storage medium by the constantly operating receiver. Theplay command 702 is followed by CRID (Ci) 703 as an identifier uniquelyidentifying the content to follow. The identifier 703 is followed by adecryption key KDi 704 allowing the encrypted content to be decrypted.The decryption key KDi 704 is then followed by data 705 about anothercontent 100 but other than the content, such as liner notes and voicecommentaries. The data 705 are in turn followed by another play command,and so on.

FIG. 5 is a flowchart of steps performed by the receiving side receivingwhat has been transmitted as described above by the transmitting side.It is assumed that the receiver is constantly in operation. In the timeperiod A, the encrypted content 100 is received and stored (in step301). At a predetermined time in the time period B subsequent to thetime period A, a play command is received (in step 302). The playcommand causes the content 100 to be decrypted and played back at thesame time (in step 303).

FIG. 6 is a block diagram of a typical broadcast receiver that carriesout the receiving steps described above. The receiver comprises: aprocessor 401 that performs decryption of contents and other processes;a receiver 402 that inputs liner nodes, voice commentaries and playcommands; an audio visual output device 403 that outputs contents, linernodes and voice commentaries; a content storage device 410 that storescontents; a memory 411 that temporarily holds received play commands andother data; a program storage device 412 that stores programs and dataother than contents and play commands; and a bus 413 that interconnectsthese component devices.

The receiver 402 is a satellite broadcasting receiver. However, thisinvention is not limited to satellite broadcasting but may be applied tovarious broadcasting systems such as terrestrial broadcasting,communication satellite broadcasting, and CATV. In keeping with any ofsuch setups that may be adopted, a terrestrial broadcasting receiver, acommunication satellite receiver or a set-top box may be utilized.

The audio visual output device 403 is made up of an amplifier andspeakers if the content is composed only of audio data. The outputdevice 403 may further include a monitor or other suitable display unitif the content is made up of visual data.

The content storage device 410 may be any one of such devices as a harddisc drive (magnetic disk drive), a DVD-RAM/RW drive and a flash memory.The memory 411 is typically implemented in the form of a DRAM. Theprogram storage device 412 may be any one of such devices as a hard discdrive, a flash memory and a ROM.

The process in step 301 of receiving and storing the encrypted content,shown in FIG. 5, will now be described in more detail by referring toFIG. 7. It is assumed that the receiver is constantly in operation andthat the receiver 402 is receiving broadcasts (in step 601). Theprocessor 401 processes the received information in a manner describedbelow in accordance with programs stored in the program storage device412. If the received information is not a begin store command 501, theprocessor 401 waits for the command to arrive (in step 602). Uponreceipt of the begin store command 501, the processor 401 stores anidentifier CRID(Ci) 502 following the command 501 onto the contentstorage device 410 (in step 603).

An encrypted content KEi(Ci) 503 received following the identifier 502is then stored onto the content storage device 410 (in step 604). Atthis point, the correspondence between the identifier CRID(Ci) and thecontent KEi(Ci), which will be needed later in decrypting and playingback the content, is determined by this embodiment establishing CRID(Ci)as the name of a file in which to store KEi (Ci). That is, theidentifier CRID(Ci) is stored as directory information on the contentstorage device 410.

The encrypted content KEi(Ci) is stored continuously until an end storecommand 504 is received (in step 605). Upon receipt of the end storecommand 504, the processor terminates the process of receiving andstoring the encrypted content 100 (in step 606).

The process in step 302 of receiving a play command and the process instep 303 of decrypting and playing back the encrypted content, shown inFIG. 5, will now be described in more detail by referring to FIG. 8. Itis assumed that the receiver is constantly in operation and that thereceiver 402 is receiving broadcast information (in step 800). Theprocessor 401 processes the received information in a manner describedbelow in accordance with programs stored in the program storage device412. If the received information is not a play command 702 (in step801), the processor sends out the information without performing anyadditional processing. The information in this case is made up of linernotes and voice commentaries on the content 100. If the receivedinformation turns out to be a play command 702, the processor storesinto the memory 411 an identifier CRID(Ci) 703 and a decryption key 704transmitted following the command 702 (in step 803).

Based on the identifier CRID(Ci) 703, the processor identifies andretrieves the encrypted content from the content storage device 410 (instep 804). With this embodiment, the file having a file name of CRID(Ci)703 is an encrypted content file. The processor then decrypts theencrypted content using the decryption key KDi 704 held in the memory(in step 805) and outputs the decrypted content to the audio visualoutput device 403 (in step 806). After the output, the processor deletesthe decryption KDi 704 from the memory (in step 807).

Where the processing above is performed, the receiver has only theencrypted content 100 retained therein at any time except at apredetermined playback time, whereby the content is protected againstunauthorized decryption and reproduction. For playback, a play command,an identifier CRID(Ci) 703 and a decryption key KDi 704 need only bebroadcast. That means a narrow band width is sufficient for the purpose.

After viewing a content, a user may want to purchase that content. Inthat case, the user may buy only the decryption key KDi 704 over asuitable network.

Although the embodiment above has been described as distributingcontents by utilizing all band widths dedicated to data broadcasts, thisis not limitative of the invention. If the contents to be sent are notlarge enough in data size to occupy the entire band widths, only thoseband widths commensurate with the data size may be employed. Theinvention is not limited to using data broadcasts; it may also beimplemented by utilizing spare time periods in TV and radio broadcasts.

As described and according to the invention, an encrypted content istransmitted in a time period such as midnight when ordinary broadcastcontents are not distributed, so that the encrypted content is storedand later decrypted for playback by subsequent transmission of textinformation of a limited data size, a play command, an identifier foridentifying the content in question, and a decryption key. This methodallows contents to be broadcast using a narrow band width and playedback in a sequence and in a manner predetermined by the distributingparty.

Where the same content such as a commercial is to be broadcast a numberof times during a given broadcast time period, the content need only bebroadcast once for storage, followed by a play command, a contentidentifier and a decryption key transmitted as many times as desired.

Because the decryption key is transmitted exactly when the contentcorresponding to the key is to be played back from storage and becausethe key is deleted the moment the playback is terminated, the content isenjoyed only during the time period predetermined by the distributingparty and not in any other time period. This feature protects contentsagainst unauthorized decryption and playback.

If users wishes to purchase a content, they need only buy in a suitablemanner a decryption key corresponding to the content in question.

While the present invention has been described above in conjunction withthe preferred embodiments, one of ordinary skill in the art would beenabled by this disclosure to make various modifications to thisembodiment and still be within the scope and spirit of the invention asdefined in the appended claims.

1. A distributing method comprising the step of: distributing encryptedcontents from a distributing side wherein said encrypted contents areencrypted by said distributing side and said encrypted contents arestored into a storage medium at a receiving side; and distributing aplay command with a decryption key at a time after distributing saidencrypted contents to cause the encrypted contents to be played, whereinthe time at which the play command and decryption key are distributed ispredetermined by said distributing side and said decryption key isstored into a memory at a receiving side; wherein, upon receiving saidplay command, the receiving side causes said encrypted contents to beretrieved from said storage medium and said decrypted using saiddecryption key to produce decrypted contents, and wherein the decryptedcontents are outputted and said decryption key is deleted from saidmemory when output of said decrypted content is finished, wherein saidencrypted contents are distributed with a first identifier identifyingsaid encrypted contents, and wherein said play command is distributedwith a second identifier identifying said first identifier to indicatesaid encrypted contents to be retrieved from said storage medium foroutput.
 2. A distributing method according to claim 1, wherein saidencrypted contents distributed in a first time period include an endstore command for terminating the storing of said contents into saidstorage medium.
 3. A distributing receiver comprising: a receiving unitwhich receives encrypted contents, which is encrypted by a distributingside, and which is distributed from the distributing side, and receivesa play command with a decryption key at a time after distributing saidencrypted contents to cause the encrypted contents to be played, whereinthe time at which the play command and decryption key are distributed ispredetermined by said distributing side; a storage medium which storessaid encrypted contents; a memory which stores said decryption key; aprocessor which stores said encrypted contents into said storage medium,stores said decryption key into said memory, retrieves said encryptedcontents from said storage medium in accordance with said play command,decrypts said encrypted contents by using said decryption key stored insaid memory, outputs decrypted contents, and deletes said decryption keyfrom said memory when output of said decrypted contents is finished,wherein said encrypted contents are distributed with a first identifieridentifying said encrypted contents, and wherein said play command isdistributed with a second identifier identifying said first identifierto indicate said encrypted contents to be retrieved from said storagemedium for output.
 4. The distributing receiver according to claim 3,wherein said encrypted contents distributed in a first time periodinclude an end store command for terminating the storing of saidcontents into said storage medium.
 5. The distributing receiveraccording to claim 4, wherein the processor terminates the storing ofsaid encrypted contents into said storage medium at a time when said endstore command is received.
 6. The distributing receiver according toclaim 3, wherein the processor finds a store start command and storessaid encrypted contents subsequent to said store start command into saidstorage medium.
 7. The distributing receiver according to claim 4,wherein the processor finds a store start command and stores saidencrypted contents subsequent to said store start command into saidstorage medium.
 8. A distributing method comprising the step of:distributing encrypted contents from a distributing side wherein saidencrypted contents are encrypted by said distributing side and saidencrypted contents are stored into a memory storage unit at a receivingside; and distributing a play command with a decryption key at a timeafter distributing said encrypted contents to cause the encryptedcontents to be played, wherein the time at which the play command anddecryption key are distributed is predetermined by said distributingside and said decryption key is stored into said memory storage unit ata receiving side; wherein, upon receiving said play command, thereceiving side causes said encrypted contents to be retrieved from saidmemory storage unit and decrypted using said decryption key to producedecrypted contents, and wherein the decrypted contents are outputted andsaid decryption key is deleted from said memory storage unit when outputof said decrypted content is finished, wherein said encrypted contentsare distributed with a first identifier identifying said encryptedcontents, and wherein said play command is distributed with a secondidentifier identifying said first identifier to indicate said encryptedcontents to be retrieved from said memory storage unit for output.
 9. Adistributing method according to claim 8, wherein said encryptedcontents distributed in a first time period include an end store commandfor terminating the storing of said contents into said memory storageunit.
 10. A distributing receiver comprising: a receiving unit whichreceives encrypted contents, which is encrypted by a distributing side,and which is distributed from the distributing side, and receives a playcommand with a decryption key at a time after distributing saidencrypted contents to cause the encrypted contents to be played, whereinthat time at which the play command and decryption key are distributedis predetermined by said distributing side; a memory storage unit whichstores said encrypted contents and said decryption key; a processorwhich stores said encrypted contents into said memory storage unit,stores said decryption key into said memory storage unit, retrieves saidencrypted contents from said memory storage unit in accordance with saidplay command, decrypts said encrypted contents by using said decryptionkey stored in said memory storage unit, outputs decrypted contents, anddeletes said decryption key from said memory storage unit when output ofsaid decrypted contents is finished, wherein said encrypted contents aredistributed with a first identifier identifying said encrypted contents,and wherein said play command is distributed with a second identifieridentifying said first identifier to indicate said encrypted contents tobe retrieved from said memory storage unit for output,
 11. Thedistributing receiver according to claim 10, wherein said encryptedcontents distributed in a first time period include an end store commandfor terminating the storing of said contents into said memory storageunit.
 12. The distributing receiver according to claim 11, wherein thesaid processor terminates the storing of said encrypted contents intosaid memory storage unit at a time when said end store command isreceived.
 13. The distributing receiver according to claim 10, whereinthe processor finds a store start command and stores said encryptedcontents subsequent to said store start command into said memory storageunit.
 14. The distributing receiver according to claim 11, wherein theprocessor finds a store start command and stores said encrypted contentssubsequent to said store start command into said memory storage unit.